Interferon inducers or semipurified preparations of interferon administered in vivo or in vitro enhance macrophage functions such as spreading on inert substrates or phagocytic activity. In certain model systems cytotoxicity towards target cells may be also stimulated. Because of the relevance of macrophages to clearance of pollutants, and host responses to microorganisms and tumors, the mechanisms involved, in the effects of interferon inducers and interferon on macrophages need to be further evaluated. In particular, more stringent evidence is required that the effects are indeed mediated by interferon. We purpose: 1) to obtain monoclonal antibodies to mouse interferon by the hybridoma technique in order to acquire specific reagents able to functionally inactivate type I (viral) interferon. Liposome entrapped interferon preparations will be used for immunization in order to increase the number of specific B-cell precursors in the spleen; 2) to compare the features and requirements for in vitro phagocytic stimulation with those for the acquisition of the antiviral state in macrophages. Specifically, to evaluate the role of priming with interferon and of protein and RNA synthesis on the acquisition and decay of the phagocytic enhancement by interferon preparations, 3) to examine the endocytic effects of interferon preparations on inflammatory or activated macrophages; 4) to determine whether phagocytosis by other cells, such as macrophage-like lines, polymorphonuclear neutrophils or fibroblasts is similarly affected by interferon preparations.